Core taking apparatus



Jan. 15, 1952 J. c. S TOKES CORE TAKINQ APPARATUS Filed April 4, 1949 1/0/1/7 C. Jfo/res IN l/[NTOH I A 7' TOR/V5 )J Patented Jan. 15, 1952 CORE TAKING APPARATUS John C. Stokes, Houston, Tex;, assignorto Reed Roller -Bit Company,l-ouston, Tex., a corporati'on'of Texas Application April 4, 1949',Ser'ial No. 85,409

'Claims. 1 This invention relates to new and useful improvements in core taking apparatus andrelates particularly to core "apparatus of the removable yp In "the use of removable or retrievable core taking-apparatus it has become the general practice to drop the inner core barrel assembly downwardly through the drill pipe with said assembly falling downwardly by gravity to a final seated position within the lower portion of the drill pipe and with its pilot or core drill projecting outwardly through the outer bit. Ordinarily, an annular stop seat or'shoulder is formed at some point in the lower portion of the drill pipe or in the Outer'bit and the inner core "barrel assembly is provided with an external shoulder which is adapted to engage the stop seat or shoulder. It will be evident that when the core barrel assembly is dropped and falls by gravity, the abrupt halt of the assembly caused by the engagement of its external shoulder with the stop seat will result in an excessive jar or impact which may damage the assembly.

It is therefore one object of this invention to provide an improved core barrel apparatus wherein shock absorbing means is associated with the inner core barrel assembly to eliminate damage to the assembly due to excessive impact or jar caused by seating of the assembly in its final position within the drill pipe.

An important object of the invention is to provide an improved core taking apparatus having an annular stop seat within the drill pipe which is arranged to be engaged by an external shoulder on the inner core barrel assembly together with a fluid type shock absorber which will automatically function just prior to the engagement of the shoulder on the core barrel assembly with the stop seat, whereby the assembly may be dropped and may fall rapidly through the drill pipe to a point closely adjacent to the stop seat and will then have its movement halted or slowed down to a point where excessive shock or impact is eliminated.

Still another object is to provide an apparatus of the character describedwl'lereinthe fluid within a cylinder functions to absorb the shock or 'jar occasioned by the inner core barrel a'ssenibly'bei-ng dropped by gravity through the drill pipe and also wherein the core barrel assembly is provided with a piston. coacting with the cylinder to gradually discharge the fluid at 'a controlled rate, thereby allowing the core barrel assembly to be slowly moved to its final seated position within the drill pipe.

Other and further objects of the invention will appear from the description of the invention.

In the accompanying drawings, which form a part of the instant specification, which are to 'be read in conjunction therewith and wherein like reference numerals are used to indicate like parts in the various views:

"Figure '1 is a view partly in section and partly in elevation of an improved core taking apparatus constructed in accordance with the invention and illustrating the inner core barrel assembly mounted in its final seated position within'the drill pipe,

Figure 2 is a transverse sectional view of the core taking apparatus and showing the inner core barrel assembly spaced upwardly from its finalseatedpositionyaml Figure 3 is ahorizontal cross-sectional view taken on the line -3-3of Figure '2.

the drawings, the numeral Ill designates the "usual drill pipewhich is connected by means of an elongate drill collar H and connecting sub 'i'2with an 'outer drill bit 18. The drill bit is of any'sui'ta'ble construction and is formed with an axial bore :M extending therethrough. The upper end of :said bore is enlarged to provide an internal annular supporting "shoulder I 5 within the bit body.

relatively elongate cylinder-"or sleeve 16 is formed with radially directed projections or ribs 47 and the-latter extend from the lower end of "the cylinder or'sleeve to a point terminating short of the upper end thereof. The radial ribs or projections are adapted to slidably fit within the lower portion ofthe bore [4 of the bit 13 and reach -rib is provided with an external shoulder 38 which engages'the internal-supporting shoulder 15 within the bit bore. This arrangement disposes the cylinder'or sleeve 15 axially within the bore of the bit and the cylinder is retained in position against upward displacement by means of 'a snap ring '59 which engages within an iannular'groove '20 in the wall of the bore [4 of the bit "and has a portion thereof overlying the upper surfaces of the radial ribs or projections 11. "The longitudinalspaces between the radial ribs or projections i1 fform longitudinal flow passages 21 whereby fluid may becirculate'd downwardly around the cylinder or sleeve 16.

Thecyl'inderbr'sleeve 16 has an axial bore 22 extending entirely therethrough and the upper portion'of the bone is counter-bored at 23 to form an "internal annular stop seat or shoulder 24 within the cylinder. The shoulder is spaced downwardly from the upper end of the cylinder.

A removable or retrievable core barrel assembly A is adapted to be dropped downwardly through the drill pipe and includes an elongate core barrel having the usual latching mechanism 26 at its upper end. A core or pilot bit 2'! of any desired construction is attached to the lower end of the assembly and interposed between the bit 2'! and the core barrel is a shock absorbing piston 23. The piston has its lower portion of an external diameter which is substantially the same as the external diameter of the pilot or core bit 21; both the bit and said lower portion of the piston ar of substantially the same diameter as the bore 22 of the sleeve or cylinder I8.

The upper portion 28a of the piston has an external diameter which is slightly-less than the diameter of the counter-bore 23 of the cylinder or sleeve and an external shoulder 29 is formed on the piston between said enlarged upper portion 28a, and the smaller or reduced lower portion of the piston. When the enlarged upper portion 28a of the piston enters the counter-bore 23 of the cylinder or sleeve there is only a slight clearance between the parts with the result that any fluid which may be in the upper portion of the cylinder must escape upwardly around the portion 28a of the piston. By varying the relative sizes of the upper portion 28a of the piston and the diameter of the counter-bore 23, the rate of escape of fluid between these parts may be controlled and thus the rate of movement of the assembly after the upper portion of the piston first enters the counter-bore may be controlled.

In the operation of the device the cylinder or sleeve 56 is mounted within the outer bit l3 in the manner described and is thus disposed axially within the bore of said outer bit. The bore of the drill bit as well as the well bore is of course filled with the usual mud or fluid which is standing therein. The inner core barrel assembly A is then dropped downwardly through the drill pipe Ill and will fall downwardly by gravity through said pipe. The pilot or core bit 21 will pass downwardly through the cylinder l6 and as soon as the enlarged upper portion 280, of the piston 28 enters the upper end of the counterbore 23; some fluid is immediately trapped between the external shoulder 29 on the piston and the internal shoulder 24 within the cylinder.

'This fluid will provide a cushion which will immediately resist further dropping of the assembly A. The trapped fluid may escape through the relatively small annular space surrounding the upper portion 28a of the piston and the weight of the assembl A will be suflicient to force the fluid outwardly through this space. However, it

'is apparent that continued movement of the assembly after the initial entry of the enlarged upper portion of the piston into the counter-bore will be relatively slow, whereby the assembly is more or less gradually moved to its final seated position, in which position the external shoulder of the piston is seated on the internal stop seat 24 within the cylinder.

It is thus apparent that the provision of the lcylinder II; which is disposed axially within the lower portion of the drill pipe and the co-acting piston 28 which forms part of the inner core barrel assembly assures that the assembly A will not strike the stop shoulder or seat 24 with an excessive impact or jar. The fluid which is 1 trapped between the shoulders 24 and 29 as the enlarged portion 28a of the piston first enters the counter-bore 23 of the cylinder functions as a shock absorbing means which cushions the downwardly falling assembly A sets up a resistance to further lowering. After the initial impact is cushioned or absorbed, the gradual escape of the trapped fluid around the piston will allow the assembly to slowly move to its finally seated position. The assembly A is thus protected from excessive jar or impact which permits said assembly to be dropped so as to fall downwardly through the drill pipe by gravity without any danger of damage to the assembly or to the shoulder 29 on said assembly or the stop seat 24 within the cylinder. The particular shock absorbing means may be readily applied to any well-known retrievable core-taking assembly which is now in general use and the invention is not to be limited to use with the particular assembly A which is illustrated herein.

From the foregoing it will be seen that this invention is one well adapted to attain all the ends and objects hereinabove set forth together with other advantages which are obvious and which are inherent to the structure and process.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and sub-combinations. This is contemplated by and is within the scope of the claims.

As many possible embew ents may be made of the invention without depal ting from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

Having described the invention, I claim:

1. A shock absorbing device for retrievable core-taking apparatus including a fluid filled cylinder having an imperforate wall mounted within a drill pipe, an internal seat within the cylinder whereby the bore of the cylinder above the seat is enlarged, and a piston mounted on the core barrel for co-acting with said cylinder to cushion the shock caused by dropping of the apparatus through the drill pipe, said piston having a shoulder engageable with said seat and said cylinder being located to receive the piston just prior to the final positioning of the core taking apparatus within the drill pipe.

2. A shock absorbing device as set forth in claim 1, wherein the external diameter of the piston is slightly smaller than the bore of the cylinder, whereby the fluid is forced from the upper end of the cylinder through this restricted annular space so that final movement of the apparatus is at a slow rate.

3. The combination with a drill pipe having an open ended cylinder mounted therein with a supporting shoulder within the bore of the cylinder with the annular wall of the cylinder above the shoulder being imperforate, of an inner core barrel assembly having a piston connected thereto, with said piston having an external shoulder and with the portion of said piston above the shoulder being of a diameter less than the bore of the cylinder above the seat, whereby entrance of the piston into the cylinder functions as a shock absorbing means to retard movement of its ends whereby the bore of the cylinder above U the seat is enlarged, a piston mounted on the lower end of the core barrel having a reduced lower end whereby an external shoulder is formed on the piston, the lower end of the piston having a diameter substantially equal to the diameter of the cylinder below the seat and having an external diameter above the external shoulder which is slightly smaller than the enlarged upper end of the bore of the cylinder.

5. A shock absorbing device as set forth in 10 claim 4, wherein the exterior of the cylinder is provided with longitudinal fiuid passages which permit a flow of fluid between the cylinder and the bore of the drill bit when the cylinder is in position within said bit.

JOHN C. STOKES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,948,631 Robichaux et a1. Feb. 2'7, 1934 2,046,106 Bozeman June 30, 1936 2,068,762 Pennington Jan. 26, 1937 2,079,941 Labarre May 11, 1937 2,412,915 Sewell Dec. 17, 1946 

